N° 2019-15 Distinguishing Incentive from Selection Effects in Auction
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Série des Documents de Travail n° 2019-15 Distinguishing Incentive from Selection Effects in Auction-Determined Contracts Laurent LAMY1 Manasa PATNAM2 Michael VISSER3 Les documents de travail ne reflètent pas la position du CREST et n'engagent que leurs auteurs. Working papers do not reflect the position of CREST but only the views of the authors. 1 CIRED, Ecole des Ponts, ParisTech. E-mail : [email protected] 2 IMF. E-mail : [email protected] 3 CREST; ENSAE; CRED, University of Paris 2. E-mail : [email protected] Distinguishing Incentive from Selection Effects in Auction-Determined Contracts ∗ Laurent Lamy† Manasa Patnam ‡ Michael Visser§ September 20, 2019 Abstract This paper develops a novel approach to estimate how contract and principal-agent characteristics influence an ex-post performance outcome when the matching between agents and principals derives from an auction process. We propose a control-function ap- proach to account for the endogeneity of contracts and matching. This consists of, first, estimating the primitives of an interdependent values auction model - which is shown to be non-parametrically identified from the bidding data - second, constructing control func- tions based on the distribution of the unobserved private signals conditional on the auction outcome. A Monte Carlo study shows that our augmented outcome equation corrects well of the endogeneity biases, even in small samples. We apply our methodology to a labor market application: we estimate the effect of sports players’ auction-determined wages on their individual performance. Keywords: Econometrics of Contracts, Econometrics of Auctions; Structural Econometrics; Endogenous Matching; Polychotomous Sample Selection; Wage-Performance Elasticity. JEL classification: C01; C29 ; C57; D44; M52; Z22. ∗We thank James Albrecht, Shekar Shankar Aiyar, Mitali Das, Kartikeya Date, Xavier d’Haultfoeuille, Aureo de Paula, Guido Kuersteiner, Ingmar Prucha, Paul Scott, Ali Skalli, Andrew Sweeting, Frank Vella and seminar partici- pants at CREST, Georgetown University, the University of Besançon, the University of Luxembourg, the University of Maryland, the University of Paris II, the 2nd ECODEC Conference, the 7th French Econometrics Conference, and the 46-th EARIE conference, for helpful comments and suggestions. We thank Arun Kumar for excellent research assistance. This paper is a major revision of a draft which circulated under the title “Correcting for Sample Selec- tion From Competitive Bidding, with an Application to Estimating the Effect of Wages on Performance.” Financial support from the LABEX ECODEC (ANR-11-IDEX-0003/Labex Ecodec/ANR-11-LABX-0047) is gratefully acknowl- edged. †CIRED (Ecole des Ponts, ParisTech). Email: [email protected]. ‡IMF. Email: [email protected]. §ENSAE-CREST and CRED, University of Paris 2. Email: [email protected]. 1 1 Introduction A central issue in the empirical literature on contracts concerns quantifying the effect of con- tract characteristics on observed behavior. These characteristics influence ex-post outcomes through two kinds of channels: on the one hand, they offer a variety of incentives to elicit efforts from the contracting parties; on the other, they play a key role in the way agents and principals match together according to both observable and unobservable characteristics. For instance, to reduce the cost of monitoring, a firm can decide to raise salaries, which, by making the unemployment threat more costly, should incite workers to exert more effort (Shapiro and Stiglitz (1984)). However, the wage increase also changes the pool of workers that are matched to the firm, in particular on the basis of unobserved worker characteristics, including those that create idiosyncratic synergies between workers and firms (Abowd et al. (1999)). Similarly, re- cent empirical work on procurement contracts awarded through competitive tendering have stressed the importance of both ex-post moral hazard and adverse selection (Lewis and Ba- jari (2011), Decarolis (2014)): agents’ ex-post performance (like the project-delivery time or the quality of realized work) is driven by the contract characteristics (part of which may be en- dogenously determined at the procurement auction)1 both directly through incentives schemes (like penalties for delays) and indirectly through the fact that contract characteristics have a screening effect (e.g., the ability of a firm to complete the project on time may be correlated with its winning probability). An assessment of the relative magnitude of incentive and adverse selection effects is crucial when deriving either optimal contracting choices or optimal market regulation (Laffont and Tirole (1993)). In the empirical contract literature, most papers focus on the “incentive effect” of contracts. These effects are typically identified using exogenous variations in contract characteristics, by way of field or natural experiments. Such an approach is particularly popular in the labor literature, e.g., to estimate whether better paid workers reciprocate (Gneezy and List (2006), Mas (2006), Lee and Rupp (2007)), or to measure to what extent salaries on the basis of realized output (like piece-rates wages or sharecropping arrangements) enhance performance ceteris paribus (Lazear (2000), Shearer (2004), Burchardi et al. (2019)). Although quantifying incentive effects is admittedly interesting, it is by itself not sufficient to answer many important policy questions. If one wishes to measure for instance the impact on a principal’s payoff of using an alternative class of contracts, or to evaluate the welfare effect of a new regulation, then counterfactual calculations are necessary. Such calculations require in turn that the distribution of agents’ unobserved characteristics is known. They furthermore require knowledge of how self-selection of agents to contracts is determined given these un- observed variables. Distinguishing incentive from selection effects is, however, a challenging 1 In the so-called ‘A+B’ design analyzed by Lewis and Bajari (2011), construction firms not only submit a dollar bid (for materials and labor) but also a duration in days to complete the project which determines how penalties for delays are computed. 2 issue as stressed by Chiappori and Salanié (2003). This issue has been addressed when a monopolistic principal posts a contract (or a menu of contracts) to the agents who decide first whether to match with the principal and second chose their level of effort or consumption, and this optimally given their privately observed character- istics. To identify such models, two kinds of approaches have been developed in this literature: One strand relies on exogenous variations of the contracts posted by the principal (Powell and Goldman (forthcoming), d’Haultfoeuille and Février (forthcoming)). Another assumes that the contract posted by the principal is optimal and relies then explicitly on the correspond- ing first-order conditions. The seminal theoretical contribution in this field is Perrigne and Vuong (2011) who establish the non-parametric identification of Laffont and Tirole (1986)’s procurement model from the observation of the contract’s realization (the quantity demanded, the production costs and the associated transfers). Perrigne and Vuong (2011) show how to distinguish in the realized production costs what comes from the ex-ante type of the agent (capturing the effect of adverse selection), the agent’s effort (driven by the incentives asso- ciated to the chosen contract), and the ex-post exogenous shocks affecting final demand and (observed) production costs.2 While this literature considers typically uni-dimensional types as in the bulk of auction and contract theory, some recent contributions have dealt with contract models involving multidimensional types (Luo et al. (2012), Aryal et al. (2019)). In many environments, however, there are multiple principals to be matched with the various agents. This paper develops a new methodology to consistently estimate how contract and principal-agent characteristics influence agents’ ex-post performance when the matching of agents to principals and part of the contract characteristics are determined through auctions.3 We present our methodology through the labor auction framework that we use later as an empirical illustration: to buy the services of workers, firms participate to a centralized auction market that assigns each worker to the winning bidder (if any) and where the winning bid determines the wage.4 Nevertheless, we should keep in mind that our methodology can be applied very broadly. The main features of our setup are the following: An ex-post measure of each worker’s per- formance is observed. Besides firm-worker observable characteristics, this measure is assumed to depend on the wage (the incentive effect) and also on two signals. The first signal reflects idiosyncratic worker-firm synergies, observed privately by the firm concerned, and the second one reflects attributes that are commonly valued by all firms, observed by the firm previously 2See Paarsch and Shearer (2000) and Gayle and Miller (2015) for the estimation of related agency models applied to labor contract data, and Perrigne and Vuong (2011) for additional references, in particular regarding contractual arrangements in agriculture, corporate finance, credit markets, insurance and retailing. 3We consider thus a class of models where the matching process involves “market power”. This contrasts with the frictionless two-sided matching models